Until Paperless Post.
As you can see from this sample wedding invitation, the quality of experience on these is far above the rest -- and such pretty designs, too. Although they're still in beta, I've used them for birthdays, Mother's Day, all sorts of things I never imagined using an e-card for, with great success. I wouldn't go so far as to use them for weddings, graduations, or baby announcements, the real "milestone" events... but for parties, holidays, etc.? I think I'm sold. And even if you run through your free initial set of "stamps" (the currency at this site), refills are very affordable.
If you're interested, you can sign up here.